From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 487B6C0650E for ; Wed, 3 Jul 2019 14:52:25 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 219EE21881 for ; Wed, 3 Jul 2019 14:52:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 219EE21881 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:36570 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1higcS-0000RJ-Bq for qemu-devel@archiver.kernel.org; Wed, 03 Jul 2019 10:52:24 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:60879) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1higb9-0007Ms-Re for qemu-devel@nongnu.org; Wed, 03 Jul 2019 10:51:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1higb7-0004d0-Sn for qemu-devel@nongnu.org; Wed, 03 Jul 2019 10:51:03 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47422) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1higb2-0004Yy-Lk; Wed, 03 Jul 2019 10:50:57 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9BB5031628E6; Wed, 3 Jul 2019 14:50:55 +0000 (UTC) Received: from [10.3.116.152] (ovpn-116-152.phx2.redhat.com [10.3.116.152]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C3AB17C635; Wed, 3 Jul 2019 14:50:52 +0000 (UTC) To: Maxim Levitsky , qemu-devel@nongnu.org References: <20190630150855.1016-1-mlevitsk@redhat.com> <20190630150855.1016-2-mlevitsk@redhat.com> From: Eric Blake Openpgp: preference=signencrypt Autocrypt: addr=eblake@redhat.com; keydata= xsBNBEvHyWwBCACw7DwsQIh0kAbUXyqhfiKAKOTVu6OiMGffw2w90Ggrp4bdVKmCaEXlrVLU xphBM8mb+wsFkU+pq9YR621WXo9REYVIl0FxKeQo9dyQBZ/XvmUMka4NOmHtFg74nvkpJFCD TUNzmqfcjdKhfFV0d7P/ixKQeZr2WP1xMcjmAQY5YvQ2lUoHP43m8TtpB1LkjyYBCodd+LkV GmCx2Bop1LSblbvbrOm2bKpZdBPjncRNob73eTpIXEutvEaHH72LzpzksfcKM+M18cyRH+nP sAd98xIbVjm3Jm4k4d5oQyE2HwOur+trk2EcxTgdp17QapuWPwMfhaNq3runaX7x34zhABEB AAHNHkVyaWMgQmxha2UgPGVibGFrZUByZWRoYXQuY29tPsLAegQTAQgAJAIbAwULCQgHAwUV CgkICwUWAgMBAAIeAQIXgAUCS8fL9QIZAQAKCRCnoWtKJSdDahBHCACbl/5FGkUqJ89GAjeX RjpAeJtdKhujir0iS4CMSIng7fCiGZ0fNJCpL5RpViSo03Q7l37ss+No+dJI8KtAp6ID+PMz wTJe5Egtv/KGUKSDvOLYJ9WIIbftEObekP+GBpWP2+KbpADsc7EsNd70sYxExD3liwVJYqLc Rw7so1PEIFp+Ni9A1DrBR5NaJBnno2PHzHPTS9nmZVYm/4I32qkLXOcdX0XElO8VPDoVobG6 gELf4v/vIImdmxLh/w5WctUpBhWWIfQDvSOW2VZDOihm7pzhQodr3QP/GDLfpK6wI7exeu3P pfPtqwa06s1pae3ad13mZGzkBdNKs1HEm8x6zsBNBEvHyWwBCADGkMFzFjmmyqAEn5D+Mt4P zPdO8NatsDw8Qit3Rmzu+kUygxyYbz52ZO40WUu7EgQ5kDTOeRPnTOd7awWDQcl1gGBXgrkR pAlQ0l0ReO57Q0eglFydLMi5bkwYhfY+TwDPMh3aOP5qBXkm4qIYSsxb8A+i00P72AqFb9Q7 3weG/flxSPApLYQE5qWGSXjOkXJv42NGS6o6gd4RmD6Ap5e8ACo1lSMPfTpGzXlt4aRkBfvb NCfNsQikLZzFYDLbQgKBA33BDeV6vNJ9Cj0SgEGOkYyed4I6AbU0kIy1hHAm1r6+sAnEdIKj cHi3xWH/UPrZW5flM8Kqo14OTDkI9EtlABEBAAHCwF8EGAEIAAkFAkvHyWwCGwwACgkQp6Fr SiUnQ2q03wgAmRFGDeXzc58NX0NrDijUu0zx3Lns/qZ9VrkSWbNZBFjpWKaeL1fdVeE4TDGm I5mRRIsStjQzc2R9b+2VBUhlAqY1nAiBDv0Qnt+9cLiuEICeUwlyl42YdwpmY0ELcy5+u6wz mK/jxrYOpzXKDwLq5k4X+hmGuSNWWAN3gHiJqmJZPkhFPUIozZUCeEc76pS/IUN72NfprZmF Dp6/QDjDFtfS39bHSWXKVZUbqaMPqlj/z6Ugk027/3GUjHHr8WkeL1ezWepYDY7WSoXwfoAL 2UXYsMAr/uUncSKlfjvArhsej0S4zbqim2ZY6S8aRWw94J3bSvJR+Nwbs34GPTD4Pg== Organization: Red Hat, Inc. Message-ID: <70330e00-ebe9-ce2a-5155-6f7e032e0aae@redhat.com> Date: Wed, 3 Jul 2019 09:50:51 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190630150855.1016-2-mlevitsk@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="BSNUoYfn4nUJg7mOeoHxJ6GsSQLqVT7b2" X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Wed, 03 Jul 2019 14:50:55 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH 1/1] raw-posix.c - use max transfer length / max segemnt count only for SCSI passthrough X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , Kevin Wolf , Max Reitz , qemu-block@nongnu.org, John Ferlan Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --BSNUoYfn4nUJg7mOeoHxJ6GsSQLqVT7b2 Content-Type: multipart/mixed; boundary="s2C8lxX3XGWnK5uUPhAEgRFqdj9BEnAkz"; protected-headers="v1" From: Eric Blake To: Maxim Levitsky , qemu-devel@nongnu.org Cc: Fam Zheng , Kevin Wolf , qemu-block@nongnu.org, John Ferlan , Max Reitz Message-ID: <70330e00-ebe9-ce2a-5155-6f7e032e0aae@redhat.com> Subject: Re: [Qemu-devel] [PATCH 1/1] raw-posix.c - use max transfer length / max segemnt count only for SCSI passthrough References: <20190630150855.1016-1-mlevitsk@redhat.com> <20190630150855.1016-2-mlevitsk@redhat.com> In-Reply-To: <20190630150855.1016-2-mlevitsk@redhat.com> --s2C8lxX3XGWnK5uUPhAEgRFqdj9BEnAkz Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 6/30/19 10:08 AM, Maxim Levitsky wrote: > Regular block devices (/dev/sda*, /dev/nvme*, etc) interface is not lim= ited The regular block device interface is or Regular block devices interfaces are > by the underlying storage limits, but rather the kernel block layer > takes care to split the requests that are too large/fragmented. >=20 > Doing so allows us to have less overhead in qemu. >=20 > Signed-off-by: Maxim Levitsky > --- > block/file-posix.c | 16 +++++++--------- > 1 file changed, 7 insertions(+), 9 deletions(-) >=20 > diff --git a/block/file-posix.c b/block/file-posix.c > index ab05b51a66..66dad34f8a 100644 > --- a/block/file-posix.c > +++ b/block/file-posix.c > @@ -1038,15 +1038,13 @@ static void raw_reopen_abort(BDRVReopenState *s= tate) > s->reopen_state =3D NULL; > } > =20 > -static int hdev_get_max_transfer_length(BlockDriverState *bs, int fd) > +static int sg_get_max_transfer_length(BlockDriverState *bs, int fd) > { > #ifdef BLKSECTGET > int max_bytes =3D 0; > - short max_sectors =3D 0; > - if (bs->sg && ioctl(fd, BLKSECTGET, &max_bytes) =3D=3D 0) { > + > + if (ioctl(fd, BLKSECTGET, &max_bytes) =3D=3D 0) { > return max_bytes; > - } else if (!bs->sg && ioctl(fd, BLKSECTGET, &max_sectors) =3D=3D 0= ) { > - return max_sectors << BDRV_SECTOR_BITS; > } else { > return -errno; > } > @@ -1055,7 +1053,7 @@ static int hdev_get_max_transfer_length(BlockDriv= erState *bs, int fd) > #endif > } > =20 > -static int hdev_get_max_segments(const struct stat *st) > +static int sg_get_max_segments(const struct stat *st) > { > #ifdef CONFIG_LINUX > char buf[32]; > @@ -1106,12 +1104,12 @@ static void raw_refresh_limits(BlockDriverState= *bs, Error **errp) > struct stat st; > =20 > if (!fstat(s->fd, &st)) { > - if (S_ISBLK(st.st_mode) || S_ISCHR(st.st_mode)) { > - int ret =3D hdev_get_max_transfer_length(bs, s->fd); Is it worth delaying the fstat()... > + if (bs->sg) { > + int ret =3D sg_get_max_transfer_length(bs, s->fd); > if (ret > 0 && ret <=3D BDRV_REQUEST_MAX_BYTES) { > bs->bl.max_transfer =3D pow2floor(ret); > } > - ret =3D hdev_get_max_segments(&st); > + ret =3D sg_get_max_segments(&st); =2E..until inside the if (bs->sg) condition, to avoid wasted work for other scenarios? > if (ret > 0) { > bs->bl.max_transfer =3D MIN(bs->bl.max_transfer, > ret * getpagesize()); >=20 Reviewed-by: Eric Blake --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org --s2C8lxX3XGWnK5uUPhAEgRFqdj9BEnAkz-- --BSNUoYfn4nUJg7mOeoHxJ6GsSQLqVT7b2 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEccLMIrHEYCkn0vOqp6FrSiUnQ2oFAl0cwMsACgkQp6FrSiUn Q2qN8AgAnOr7AIX+CYBiWaV9LSuiEzVHnW7ZbaGKEh1/+GCiBeydxOzwHxIWQjJx OrueXJOMQSFKYOwxKalggQmvlpWzUEWIJma4SRCmZ0WqhKsdHX2K9X2FQnp8bbkr XgQ/FMQIFkYPkfBMgWd8OacRufNBxJtMrKdbDCJ1vvOwrtA+2VozL7RaR0UAYZsu LYyVGaM4Vg4Di6pqSVFTs1I0m6k7MPbUwFxSh7iVCIA1RN6yG97ny24f0wWPeFJD BvSCh2F/L3OlMmG0JaNHNOWCNdnXGHbW+eUabOceRVwkiZKfwZDkH00d9Zx2tgGu JnvjSCG6R9SPxj7EmKDFB8ziqWErvA== =OVZt -----END PGP SIGNATURE----- --BSNUoYfn4nUJg7mOeoHxJ6GsSQLqVT7b2--